San Lucas is a municipality in the Madriz department of Nicaragua. It lies in the country's northern highlands, near the border with Honduras, in a region of small towns and agricultural communities.
The town is located roughly 227 kilometres from Managua, the national capital, and about 8.5 kilometres from Somoto, the departmental capital and the nearest major urban centre. Its position close to Somoto places it within the wider Somoto area, known for its canyon and surrounding mountainous terrain.
San Lucas is one of several municipalities that make up the Madriz department, a largely rural administrative region in northern Nicaragua.